Handheld electronic devices, such as smartphones and tablet computers, have become popular, thereby increasing demands of charging in public places. Some public places provide free charging services, but such free services are rare due to difficulty in implementing restricted free charging services through effective control of charging durations and restricting the services to authorized entities.
On the other hand, conventional paid charging services are not popular due to complex system architecture, which may lead to high costs in establishment. As an example, conventional charging devices, which process payments using credit cards, electronic tickets, NFC (near field communication) or QR codes, cannot independently operate and require support from an additional server when providing the charging services, thereby making the capability of communication with the server a must. Coin feed is another common payment, type used in conventional charging devices. Problems with coin-feed charging devices usually reside in bulkiness and billing per use or per time-limited use.